In recent years, electronic devices having the touch panel as a member for detecting an operation by a user have been widely used for mobile terminals such as smart phones; information equipments such as tablets, calculators and ticket vending machines; home electric appliances such as microwaves, TV sets and lighting equipments; industrial equipments (FA equipments) and the like.
There are known a variety of types of those touch panels, such as a resistive film type, a capacitive type, an optical type and the like. However, touch panels of any of these types receive an operation by a user's finger or a stylus pen and, unlike push-button switches, the touch panels themselves are not physically displaced when touched. Therefore, the user may not obtain feedback to the operation to the touch panel.
There has been suggested a feedback method for generating vibration when an operation to the touch panel is detected (for example, see Patent Document 1). Patent Document 1 describes an example using a piezoelectric element as a vibration unit. The vibration unit, by expanding and contracting the piezoelectric element, may bend the touch panel, thereby the vibration is generated. In this manner, an input apparatus described in Patent Document 1 may provide a tactile sensation when the user operates the touch panel.